A New Resident, a Private Well, and a Cross-Connection Question
A 40-connection community system serves a small subdivision. A new homeowner at the end of the line has an old private well on the property and wants to keep using it for irrigation while taking drinking water from the community system. During your site visit you find the homeowner has connected the private well line to the house plumbing with a simple valve and no backflow device, and the well line also tees into a hose bib that can reach a filled swimming pool. System pressure at that end of the line drops to about 15 psi during the 6–9 a.m. peak, and the homeowner's booster pump kicks on when pressure is low. You are the only certified operator.
1. Identify the cross-connection hazards here and explain why the low-pressure peak makes them worse.
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Hazards:
- Private well tied into the public supply with only a valve. A valve is not a backflow preventer. If community pressure drops below the well's pressure, well water - of unknown bacteriological and chemical quality - can be pushed into the public main.
- Homeowner's booster pump. A booster on the customer side can create pressure higher than the main, driving water backward into the system. This is a classic backpressure hazard.
- Hose bib reaching a pool. A hose submerged in a pool is a direct cross-connection; a pressure drop can siphon pool water (with its chemicals and microbes) into the drinking-water line.
Why the peak makes it worse: At 15 psi during 6–9 a.m., the main pressure is low enough that the homeowner's booster or the well pump can exceed it, reversing flow. Low pressure is exactly when backflow happens - the hazard is dormant at high pressure and active at low pressure. The combination of a low-pressure peak, a booster pump, and an unprotected well connection is a high-risk setup that needs correction, not a note in a file.
2. What corrective actions do you require, and which are the homeowner's responsibility versus the system's?
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Homeowner's responsibility:
- Air gap or reduced-pressure-zone (RPZ) assembly between the private well and the house/public supply - a proper backflow device, not a valve. The well line must not be able to pressurize the public main.
- Remove or isolate the booster pump so it cannot backfeed the main, or install appropriate backflow protection.
- Hose-bib vacuum breakers and never leave a hose submerged in the pool.
- Possibly a physical disconnect of the well from the potable plumbing if the well is not a permitted source.
System's responsibility:
- Enforce the cross-connection control program - inspect, require the device, and verify it is tested annually by a certified tester.
- Address the low-pressure peak at the end of the line (the root driver) through flushing, looping, or pressure management so the main does not drop to 15 psi.
- Document the inspection and the required corrections, and follow up.
You cannot simply tell the homeowner to "be careful" - the device and the pressure fix are both required.
3. What if the homeowner refuses to comply? What is your authority and your next step?
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Refusal is a public-health matter, not a customer-service disagreement.
- Your authority comes from the system's cross-connection control ordinance/policy and the state's regulations; the system can require correction as a condition of service.
- Next steps: issue a written notice with a deadline, notify the primacy agency, and if the hazard remains, the system can discontinue service to that connection (following whatever notice procedure your rules require) because an unprotected cross-connection endangers all 40 connections, not just that house.
- Document the inspection, the notice, the deadline, and the agency contact.
The judgment the exam is testing: you do not have the option of ignoring it because the homeowner objects. One unprotected cross-connection can contaminate the whole system, and your duty runs to all customers.